1. Field of Invention
The present invention in propulsion lift technology relates to augmenting the airflow past an aircraft wing by exhausting gas outwardly of the body of the aircraft from a location behind the wing root in a direction substantially parallel to the wing trailing edge to induce lift on the wing and to inhibit flow separation thereby improving the effectiveness of the trailing edge flap. The resultant lift increase can be used to shorten takeoff and landing distances of the aircraft.
2. Description of Prior Art
Various schemes for increasing aerodynamic lift through blowing air at high pressure over wing surfaces have been suggested in the past. Some have been applied to actual airplanes. To distinguish the schemes from each other, one must categorize them by air jet position and by physical action.
In terms of air jet position, a distinction must be made between air jets exhausting in the same direction as the free stream, i.e. chordwise blowing and air jets exhausting substantially normal to the free stream. In the latter case, air jets exhausting normal to the lifting surface and those exhausting in spanwise direction must be distinguished. The present invention falls into the category of spanwise blowing, and further discussion is restricted to same.
Two other schemes of spanwise blowing are also known. The first involves spanwise blowing with a concentrated jet near the leading edge of a wing for the purpose of enhancing the leading edge vortex and increasing vortex lift thereby. A description of that system is contained in "Theoretical and Experimental Investigation of Vortex Lift Control by Spanwise Blowing" by J. G. Theisen and R. M. Scruggs, Lockheed, Ga., September, 1973. This concept is primarily aimed at increasing lift at high angles of attack as a necessary condition for leading edge vortex formation. However, this characteristic makes the aircraft less suitable for short takeoff and landing applications which requires substantial lift increase in the low to moderate angle of attack range. In this case, compressor bleed air is envisioned for the source of the gas to be exhausted spanwise.
The second scheme involves spanwise blowing near the hingeline of a control surface or trailing edge flap for the purpose of providing boundary layer control to prevent flow separation. A description of that system is contained in "A Study of Spanwise Blowing on the Lift of Trailing Edge Flight Controls" by Ted Dansby, Lockheed, Ga., May, 1980. In this study, spanwise blowing is restricted to preventing flow separation, and is limited to that concept.
The present invention distinguishes itself by jet location, aerodynamic action, and power source from the inventions taught in the prior art. Further, a design solution for trimming the propulsive lift-induced pitching by utilizing thrust vectoring is set forth. Also described as a secondary function of the transverse thrust nozzles is the utilization of these nozzles for thrust reversal. The synergistic effect of the total system design, incorporating transverse thrust, vectored thrust, and reverse thrust, adds to the uniqueness of this invention in providing for improved maneuverability, and optimum short takeoff and landing performance for an aircraft.
The aerodynamic action of the transverse thrust increases aircraft lift through potential flow augmentation or supercirculation achieved primarily through the entrainment into the transverse jets of the air passing about the wings of the aircraft. This flow mechanism has not been identified in prior art describing other spanwise blowing concepts. In addition, the transverse jets inhibit flow separation over the trailing edge flaps thereby improving the effectiveness of those flaps.
Another feature of the present invention includes the deflected trailing edge flaps. By designing the aircraft such that the wing trailing edge is located proximate the same longitudinal position as the engine tailpipe and the transverse nozzle, engine exhaust gas can be tapped from the tailpipe through the transverse nozzle.
By the proximity of the engine exhaust location relative to the wing trailing edges, exhaust gas is available without the requirement of ducting of hot gases from a more forward or aft location.
Still another feature of this invention is the use of a swirling jet to increase the efficiency of the jet-induced lift generation process.